1. Field of the Invention
The present invention relates to a swirl injector for an internal combustion engine, and particularly to a fuel injector for a direct injection engine, which may be either a spark injection gasoline engine or a compression ignition diesel engine, which imparts a swirling motion to the fuel during injection to improve injection characteristics and performance. The swirl injector has novel characteristics which enable adjustment of the injector""s spray pattern to the phase of the stroke cycle, and may be used with a novel on-board flow meter which provides feedback to the engine control unit for adjusting injection characteristics.
2. Description of the Related Art
In recent years there has been a renewed interest in direct injection gasoline engines due to the greater fuel economy that can be achieved with direct injection engines, both for the sake of the savings in fuel costs and for the reduction in greenhouse gases consequent on reduced hydrocarbon fuel usage. The majority of gasoline fuel injection engines still use either throttle body injection or port injection into the intake manifold. Efforts towards using direct injection in gasoline engines have been complicated by the difficulty in finding a fuel injector which is capable of producing a homogenous air-fuel mixture during early fuel injection for a full load and a stratified air-fuel mixture during late fuel injection for a partial load, by controlling a stratified air-fuel mixture over a wide range of operating loads, and by the need for a rapid and smooth switching system for switching between early and late fuel injection. See SAE Technical Paper 970540, xe2x80x9cDevelopment of Direct Injection Gasoline Enginexe2x80x9d, Harada et al., February, 1997, and SAE Technical Paper 970541, xe2x80x9cDevelopment of Gasoline Direct Injection Enginexe2x80x9d, Iwamoto et al., February, 1997.
On the other hand, diesel engines may use direct injection into the combustion chamber, injection into a precombustion chamber connected to the main combustion chamber, or injection into a swirl chamber connected to the main combustion chamber. Direct injection is used with most heavy duty, high-speed diesel engines due to its greater fuel economy. A precombustion chamber is used with most passenger vehicles because of the smoother combustion and lower noise level available, at the cost of decreased fuel economy. A swirl chamber increases fuel economy over a precombustion chamber, but requires more precise machining, engineering, and matching of components. Fuel injectors for diesel engines were largely mechanically actuated and controlled until the 1980""s. With the advent of concerns about emission controls and the development of automotive electronics, diesel engines now use electronic control modules or units to control the metering and timing of fuel delivery, although actuation of the injector plunger may still be done mechanically to develop the high injection pressures needed. A representative example is the fuel injector used in the Detroit Diesel Series 60 engine, described in Diesel Technology, Norman et al., pp. 510-512 (Goodhart-Willcox Company, Inc., 2001), in which a cam activated rocker arm depresses the injector plunger, raising the fuel pressure to unseat the needle valve, while fuel metering is controlled by a solenoid activated poppet valve. Smaller direct injection diesel engines may rely entirely on air swirl for mixing air and fuel in the combustion chamber, although some mechanical injectors for diesel engines provide for swirling the fuel as it leaves the injector.
Various solutions have been proposed to address these problems. U.S. Pat. No. Re. 34, 527, issued Feb. 1, 1994 to Yoshida et al. describes a fuel injector having helical grooves. The patent is particularly directed to the feeder wire structure for the electromagnetic structure. U.S. Pat. No. Re. 34,591, issued Apr. 26, 1994 to Yoshida et al., shows the same injector as the ""527 patent, but is directed to the submagnetic structure which controls the amount of lift.
U.S. Pat. No. 4,192,466, issued Mar. 11, 1980 to Tanasawa et al., shows a swirl injector for a diesel engine having a swirl chamber. U.S. Pat. No. 4,230,273, issued Oct. 28, 1980 to Claxton et al., describes an injector switchable between single point and multi-point injection systems. The embodiment shown in FIG. 9 has helical grooves, but appears to be a pintle type not designed for dual injection. U.S. Pat. No. 4,365,746, issued Dec. 28, 1982 to Tanasawa et al. teaches a swirl injector having helical grooves which only extend through a radial angle of 60-1000 around the needle body.
U.S. Pat. No. 4,629,127, issued Dec. 16, 1986 to Kawamura et al., teaches a fuel injector having grooves in the needle and adjusting the spray angle by adjusting the area of the gap between the valve needle and valve wall, the area of the grooves, and the angle of the grooves. U.S. Pat. No. 4,653,694, issued Mar. 31, 1987 to Noguchi et al., discloses a fuel injector in which the spray angle is adjusted by tapering the walls of the valve body and the needle, and by adjusting the lift height to vary with the load.
U.S. Pat. No. 4,721,253, issued Jan. 26, 1988 to Noguchi et al., describes a swirl injector which uses a straight passage between the needle and the valve body combined with a tangential groove to provide a spray with both angle and straight components. U.S. Pat. Nos. 4,974,565 and 5,058,549, issued Dec. 4, 1990 and Oct. 22, 1991, respectively, to Hashimoto et al., teaches a fuel injector with either tangential grooves or projections to impart swirl to the fuel spray, but uses two orifices in the nozzle to provide both wide and narrow spray angles.
U.S. Pat. No. 5,163,621, issued Nov. 17, 1992 to Kato et al., shows a fuel injector with multiple orifices in the nozzle arranged at different angles, and a needle valve tip having conical sections of different diameters, the injection angle and velocity being adjusted by varying the amount of lift. U.S. Pat. No. 5,163,621, issued Jul. 28, 1998 to Furuya et al., describes a swirl fuel injector having a conical needle tip with different diameter conical sections to adjust the spray angle by the gap between the tip and the valve seat.
U.S. Pat. No. 5,983,854, issued Nov. 16, 1999 to Machida et al., teaches a switching scheme for switching between uniform fuel mixture combustion injection on the intake stroke and stratified combustion on the compression stroke by a CPU and gate circuits which test what the load condition is. Japanese Patent No. 1,227,865, published Sep. 12, 1989 shows a fuel injector with a pilot nozzle and a main nozzle having multiple orifices, and a controller which times injections to overlap sprays from the pilot and main nozzles. Japanese Patent No. 3,033,422, published Feb. 13, 1991, teaches stratified combustion obtained by positioning of the spark plug relative to the spray pattern.
Japanese Patent No. 10,311,264, published Nov. 24, 1998, discloses an injector with helical grooves in the needle and a cylindrical element between the helical grooves and the conical tip which is termed a fuel regulator. Japanese Patent No. 11,082,229, published Mar. 26, 1999, shows a fuel injector similar to the Japanese ""264 patent, but with a countersunk groove in the base of the injector body to collect any fuel spit-back after injection.
Applicant is aware of a fuel injector designed by Applicant for Unisia Jecs Co. in 1997-98 and installed in Nissan Motor Company 2.2L engines beginning with April, 1998 with some common structural similarities to the fuel injector of the present invention. The basic construction and operational differences between the injector developed for Unisia Jecs and the fuel injector of the present invention are as follows:
1. The contact zone between the needle and the valve seat has been redesigned. The new design and sizing of the needle ball head, conical nozzle and outlet cylindrical part of the nozzle suppresses shock vibrations of the needle after valve closing to prevent post injection of fuel into the cylinder head and to remove particulate emissions observed in the Unisia Jecs injector.
2. The needle swirling channels have been redesigned. The angle of the channels has been changed from 37xc2x0 to 46xc2x0. The Unisia Jecs injector has concave channels. The present fuel injector has a rectangular profile or cross-section, with the ratio of width-to-depth of 1. 5. These changes permit a 2.3 increase of swirling (rotational) speed and simultaneously damped pulsation at 50% of the umbrella part of the spray structure, resulting in higher spray quality, i.e., the time needed to get a micro-spray is decreased to 350 xcexcs from 800 xcexcs.
3. In the Unisia Jecs injector the lifting gap was 70 xcexcm and the response time was limited by the solenoid capacity to 120 xcexcs. In the present fuel injector the lifting gap is 50 xcexcm and the response time is 60 xcexcs, resulting in a higher jet penetration speed and the swirling speed of the umbrella fraction of the spray.
4. In the Unisia Jecs injector, two voltage levels (xe2x88x927/+12V and xe2x88x925/+24V) were used to operate the injector in dual switch mode with partial and full load, respectively. With the present fuel injector, the solenoid wiring has been redesigned to provide a continuous change of the lifting force at the same voltage input of 24 or 42 volts directly from the engine power supply. The current supplied to the solenoid controls the continuous operation of the fuel load.
Some of the properties of the Unisia Jecs injector were measured and described by the Applicant in Ismailov et al., xe2x80x9cLDA/PDA measurements of instantaneous characteristics in high pressure fuel injection and swirl sprayxe2x80x9d, Experiments in Fluids, Vol. 27, pp. 1-11 (1999).
Transducers or sensors permanently mounted on engines for measuring injection characteristics have generally been limited to electromagnetic devices which measure pressure or volume, rather than optical devices, such as those described in U.S. Pat. No. 3,937,087, issued Feb. 10, 1976 to W. S. Heggie (coil wrapped around fuel pipeline which presents variable resistance for sensing tube expansion); U.S. Pat. No. 4,073,186, issued Feb. 14, 1978 to C. L. Erwin, Jr. (electromagnetic sensor); and U.S. Pat. No. 4,192,179, issued Mar. 11, 1980 to E.Yelke (piezoelectric sensor).
Optical devices for measuring fuel flow in injection systems are shown in two Japanese patents. Japanese Patent No. 8-121,288, published May 14, 1996, shows a device for measuring injection rate with a pressure sensor for measuring the force of injection and a laser Doppler anemometer for measuring velocity, and which uses a mathematical formula which relates force and velocity to flow rate. Japanese Patent No. 8-121,289, published May 14, 1996, describes a device which uses two laser Doppler anemometers, one in the main supply line, the other in a bias flow generating unit fed by a divider pipe, to measure the flow rate by a differential flow rate method. Neither of these devices show an on-board sensor with a laser diode source and PIN diode detector.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a swirl injector for an internal combustion engine solving the aforementioned problems is desired.
The swirl injector for an internal combustion engine is an electronic fuel injector for a direct injection engine, either gasoline or diesel. The injector has a housing defining a fluid channel, a needle valve disposed in the fluid channel with a spring biasing the valve to a closed position, and a solenoid disposed in the housing encircling the fluid channel. The injector has a nozzle with a conical valve seat and a cylindrical discharge orifice. The needle tip is ball shaped, and the needle body has a plurality of helical grooves which are rectangular in cross section having a width to depth ratio of 1.5:1 at about a 46xc2x0 angle adjacent the tip. The valve lift is 50 xcexcm in 60 xcexcs. The penetration, swirl speed, and pitch angle are controllable through the injection pressure, providing an enhanced fuel injector for dual mode fuel injection.
In particular, by applying a lower injection pressure (about 5.0 MPa for gasoline engines and 60.0 MPa for diesel engines), the injector provides a pitch angle (measured from the injector""s longitudinal axis to the axis of the fuel""s core jet) close to 3xc2x0, with lower penetration and swirl speeds, which provides lean fuel consumption for late injection (during the compression stroke) for a partial load, such as constant speed cruising. On the other hand, by applying a higher injection pressure (about 7.0 MPa for gasoline engines and 90.0 MPa for diesel engines), the injector provides a pitch angle close to 15xc2x0, with higher penetration and swirl speeds, which serves to concentrate the core jet on a controllable point of the piston""s surface in an ultra-short time span less than 100 xcexcs for more power for early injection (during the intake stroke) for a full load, such as acceleration from a stop or climbing a hill.
The performance and rapid response capabilities of the injector may be improved, particularly with diesel engines, by using the swirl injector in combination with a flow meter capable of measuring instantaneous volumetric flow rates or pressure gradients in the fuel pipeline.
Accordingly, it is a principal object of the invention to provide a swirl injector which provides electronic fuel injection for use in either a direct injection spark ignition (gasoline engine), or a direct injection compression ignition (diesel) engine.
It is another object of the invention to provide a swirl injector with controllable pitch angle, penetration speed, and swirl speed for use as a dual mode fuel injector capable of early injection (during the intake stroke) when under full load and late injection (during the compression stroke) when under partial load.
It is a further object of the invention to provide a swirl injector having a needle valve with a ball tip and helical grooves on the needle body adjacent the needle tip having an angle and cross sectional area adjusted to provide a fuel spray having a core jet and spray umbrella of appropriate velocity and penetration for early or late fuel injection, depending on the triggering characteristics.
Still another object of the invention is to provide a swirl injector having the needle valve lift distance and speed optimized to provide ultra-short injection speed.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.